The present invention relates to a developing apparatus, and an assembly method of a developing apparatus.
In an image forming apparatus such as a laser printer, an electrostatic latent image is formed on the surface of a photoconductor drum and developer is supplied to the electrostatic latent image from a developing apparatus, so that a developer image is retained on the surface of the photoconductor drum. The developer image is then transferred to a paper sheet, so that formation of an image on the paper sheet is achieved.
A developing apparatus comprises: a case having an opening faced to the photoconductor drum; a developing roller for retaining developer which is held in the case, and a blade (layer thickness regulating member) for regulating the layer thickness of developer to be retained by the developing roller. The developing roller is supported so as to be rotatable with a portion of the surface thereof being exposed at the opening of the case. The blade is formed to have a sheet-like shape extending in the axial direction of the developing roller, in which the upper end portion thereof is supported by the case and the lower end portion is welded by pressure welding at the surface of the developing roller. The developer in the case is supplied onto the surface of the developing roller, carried between the blade and the surface of the developing roller with the rotation of the developing roller and retained on the surface of the developing roller as a thin layer having a constant thickness. The developer retained on the surface of the developing roller is supplied to the electrostatic latent image formed on the surface of the photoconductor drum when the developer comes in contact with the surface of the photoconductor drum.
In such a developing apparatus, the developer in the case might enter the back surface (face opposite to the opposed face which is opposed to the developing roller) of the blade, run round from the back surface to the upper end portion of the blade and leak from between the upper end portion of the blade and the case. Therefore, a conventional image forming apparatus is provided with a plurality of seals, which are provided at the back surface of the blade, for preventing leakage of developer which runs round from the back surface of the blade. That is, since a clearance is generated between the seal and the back surface of the blade at a portion of a step to be formed by the back surface of the blade and a support portion, which is arranged at the back surface of the blade for supporting the blade, when the seal is arranged astride the step, a plurality of seals are arranged so as not to be formed astride the step (see Japanese Patent Application Laid-Open No. 2001-60040, for example). Moreover, a conventional image forming apparatus is provided with a blade back sealing member, which is provided at the back surface of the blade, for preventing leakage of developer which runs round from the back surface of the blade (see Japanese Patent Application Laid-Open No. 2000-75657, for example).